Exposure apparatus, device manufacturing method, maintenance method, and exposure method

ABSTRACT

An exposure apparatus can prevent disadvantages of supplying liquid of reduced cleanliness and formation of watermarks. The exposure apparatus (EX) exposes a substrate (P) by irradiating exposure light (EL) onto the substrate (P) via a projection optical system (PL) and a liquid (LQ), and includes a liquid supply mechanism ( 10 ) for supplying the liquid (LQ), and a measuring device ( 60 ) which measures a time during which the supply of the liquid from the liquid supply mechanism is stopped ( 10 ).

TECHNICAL FIELD

The present invention relates to an exposure apparatus that exposes asubstrate by irradiating an exposure light onto the substrate via aprojection optical system and a liquid, a device manufacturing method, amaintenance method, and an exposure method.

Priority is claimed on Japanese Patent Application No. 2004-033679,filed Feb. 10, 2004, the content of which is incorporated herein byreference.

BACKGROUND ART

Semiconductor devices and liquid crystal display devices aremanufactured by a procedure known as photolithography, in which apattern formed on a mask is transferred onto a photosensitive substrate.An exposure apparatus used in this photolithography process includes amask stage which supports the mask and a substrate stage which supportsthe substrate, and transfers the pattern on the mask via a projectionoptical system while constantly moving the mask stage and the substratestage. Recently, in order to deal with increasing integration of devicepatterns, there is a demand to further increase the resolution ofprojection optical devices. The resolution of a projection opticaldevice increases when the exposure wavelength being used is shorter, andwhen the projection optical system has a higher numerical aperture.Accordingly, exposure wavelengths used in projection optical systems arebecoming shorter, and their numerical aperture is increasing, year byyear. While the current mainstream exposure wavelength is the 248-nmwavelength of a KrF excimer laser, an even shorter length, the 193-nmwavelength of an ArF excimer laser, is also going into actual use.

As with the resolution, depth of field (DOF) is also important whenexposing light. Resolution R and depth of field δ are expressed by thefollowing equations.R=k ₁ ·λ/NA  (1)δ=±k ₂ ·λ/NA ²  (2)

where λ is the exposure wavelength, NA is the numerical aperture of theprojection optical system, and k₁ and k₂ are process coefficients. As isclear from Equations (1) and (2), when the exposure length λ isshortened and the numerical aperture NA is increased in order toincrease the resolution R, the depth of field δ becomes narrower.

If the depth of field δ is too narrow, it becomes difficult to match thesubstrate surface to the projection face of the projection opticalsystem, and the field margin during the exposure operation may not besufficient. As an example of a method of actually shortening theexposure wavelength while increasing the depth of field, Patent Document1 discloses the immersion method. In this immersion method, an areabetween a bottom face of the projection optical system and the substratesurface is filled with a liquid, such as water or an organic solvent, toform an immersion region, and, utilizing the fact that the wavelength ofexposure light in liquid becomes 1/n of its wavelength in air (where nis the refractive index of the liquid, and is normally approximatelybetween 1.2 and 1.6), the resolution is increased while multiplying thedepth of field n times.

Patent Document 1: PCT International Publication No. WO 99/49504

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In the mean time, in an immersion exposure apparatus, when a liquidresides in a liquid supply pipe or the like which supplies the liquid,its cleanliness may deteriorate since the liquid remains stagnant in theliquid supply pipe. When liquid of reduced cleanliness is supplied ontothe substrate and exposure and measuring processes are performed throughthis liquid, the substrate may become contaminated and precision ofexposure and measurements may deteriorate. Furthermore, for example,after collecting liquid on an image surface side of the projectionoptical system, when liquid cannot be completely collected from certainmembers, such as optical members of an image surface frontal end sectionof the projection optical system and measuring members on the substratestage, and the liquid remains there for a long time and dries, marks ofthe liquid may be formed on the predetermined members, such as theoptical members of the image surface frontal end section of theprojection optical system and measuring members on the substrate stage,and foreign particles may then stick and cause deterioration in theprecision of the exposure and measuring processes.

The present invention has been made in view of the abovementionedproblems, and an object thereof is to provide an exposure apparatuswhich can prevent the disadvantage of supplying liquid of reducedcleanliness, a device manufacturing method, a maintenance method, and anexposure method. Another object is to provide an exposure apparatuswhich can prevent marks of the liquid from being formed on members whichcontact the liquid, a device manufacturing method, a maintenance method,and an exposure method.

MEANS FOR SOLVING THE PROBLEMS

To solve the above problems, the invention uses the followingconfigurations corresponding to the embodiment shown in FIGS. 1 to 4.

An exposure apparatus of the invention exposes a substrate byirradiating exposure light onto it via a projection optical system and aliquid, and includes a liquid supply mechanism that supplies the liquid,and a measuring device which measures a time during which the supply ofthe liquid from the liquid supply mechanism is stopped.

According to the invention, by using the measuring device to measure thea time during which the supply of the liquid from the liquid supplymechanism is stopped, appropriate procedures can be performed based onthe measurement result, such as flushing the supply pipes by restartingthe liquid supply before the liquid stagnates in the supply pipes andits cleanliness decreases. Therefore, problems caused by supplyingliquid whose cleanliness has decreased after stagnation onto thesubstrate can be prevented. Furthermore, based on the measurementresult, appropriate procedures such as moistening the predeterminedmembers by supplying the liquid can be performed before marks ofremaining liquid stuck on predetermined members are formed by drying ofresidual liquid. Thus, even if there is a possibility of problems causedby stopping the supply of the liquid from the liquid supply mechanism,appropriate procedures can be performed based on the measurement result,whereby generation of such problems can be prevented.

A device manufacturing method of the invention uses the exposureapparatus described above. According to the invention, since appropriateprocedures can be performed based on the measurement result of themeasuring device which measures the a time during which the supply ofthe liquid from the liquid supply mechanism is stopped, problems causedby stopping the supply of the liquid from the liquid supply mechanismcan be prevented. Therefore, it is possible to manufacture a device witha desired performance.

A maintenance method of the invention is a maintenance method of aprojection optical system, which projects an image of a pattern via aliquid, and includes measuring the elapsed time between an immersedstate of an end face on an image surface side of the projection opticalsystem and a non-immersed state.

According to the invention, by measuring the elapsed time between animmersed state of the end face on the image surface side of theprojection optical system and the non-immersed state, based on themeasurement result, the end face of the projection optical system can bewet (moistened) by supplying the liquid before marks are formed bydrying of residual liquid. Therefore, it is possible to prevent theproblem of sticky marks being formed on the end face of the imagesurface side of the projection optical system. Thus, since appropriateprocedures can be performed based on the measurement result of theelapsed time, generation of problems caused by switching from theimmersed state to the non-immersed state can be prevented.

An exposure method of the invention uses a projection optical systemmaintained using the method described above, and exposes a substrate tolight by projecting an image of a device pattern via liquid onto thesubstrate.

According to the invention, the substrate can be reliably exposed viathe projection optical system and the liquid in state where formation ofmarks of the liquid is prevented.

ADVANTAGEOUS EFFECTS OF THE INVENTION

According to the invention, exposure precision and measurement precisioncan be reliably ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram showing an embodiment of anexposure apparatus of the invention.

FIG. 2 is a diagram showing a state where liquid supply from a liquidsupply mechanism is stopped.

FIG. 3 is a diagram showing a state where liquid supply from a liquidsupply mechanism is restarted.

FIG. 4 is a flowchart of an example of manufacturing steps of asemiconductor device.

DESCRIPTION OF THE REFERENCE SYMBOLS

-   2A End face-   10 Liquid supply mechanism-   13 Supply pipes (Flow paths)-   15 Valves-   16 Flow meters-   51 Top face (Flat face)-   60 Measuring device-   300 Reference member (Flat section)-   EL Exposure light-   EX Exposure apparatus-   LQ Liquid-   P Substrate-   PL Projection optical system-   PST Substrate stage

BEST MODES FOR CARRYING OUT THE INVENTION

An exposure apparatus of the invention will be explained with referenceto the drawings. FIG. 1 is a schematic configuration diagram showing anembodiment of an exposure apparatus of the invention.

In FIG. 1, an exposure apparatus EX includes a mask stage MST whichsupports a mask M and is movable, a substrate holder PH which holds asubstrate P, a movable substrate stage PST which holds the substrate Pon the substrate holder PH, an illuminating optical system IL whichilluminates an exposure light EL onto the mask M while it is supportedby the mask stage MST, a projection optical system PL which projects animage of a pattern of the mask M illuminated by the exposure light ELonto the substrate P which is supported by the substrate stage PST, ameasuring device (timer) 60 which measures time, a control device CONTwhich controls operations of the entire exposure apparatus EX in acentralized manner, and a storage device MRY which stores various kindsof information relating to exposure processing.

The exposure apparatus EX of this embodiment is an immersion exposureapparatus which utilizes a liquid immersion method to substantiallyshorten the exposure wavelength in order to increase the resolution andactually increase the depth of field, and includes a liquid supplymechanism 10 which supplies a liquid LQ onto the substrate P and aliquid collection mechanism 20 which collects the liquid LQ on thesubstrate P. In this embodiment, pure water is used as the liquid LQ. Atleast while an image of the pattern of the mask M is being transferredonto the substrate P, the exposure apparatus EX uses the liquid LQsupplied from the liquid supply mechanism 10 to locally form, in atleast one part of the substrate P including a projection region AR1 ofthe projection optical system PL, an immersion region AR2 which islarger than the projection region AR1 and smaller than the substrate P.Specifically, the exposure apparatus EX fills the liquid LQ in an areabetween an optical element 2 at an image surface side frontal end of theprojection optical system PL and a top face (exposure surface) of thesubstrate P, and projects an image of the pattern of the mask M onto thesubstrate P via the liquid LQ between the projection optical system PLand the substrate P, and via the projection optical system PL, therebyexposing the substrate P.

In this embodiment, an example where the exposure apparatus EX is ascanning-type exposure apparatus (so-called a scanning stepper) whichsimultaneously moves the mask M and the substrate P in differentdirections with respect to each other (opposite directions) within ascanning direction (predetermined direction) while carrying out exposureto project the pattern formed on the mask M onto the substrate P. In thefollowing explanation, a direction of synchronous motion of the mask Mand the substrate P within a horizontal plane (scanning direction, orpredetermined direction) is referred to as the X-axis direction, adirection orthogonal to the X-axis direction in the horizontal plane isreferred to as the Y-axis direction (non-scanning direction), and adirection which is perpendicular to the X-axis and Y-axis directions andmatches an optical axis AX of the projection optical system PL isreferred to as the Z-axis direction. Rotational (gradient) directionsaround the X-axis, Y-axis, and Z-axis directions are respectively termedθX, θY, and θZ directions. Note that the term “substrate” here includesone formed by coating a semiconductor wafer with a resist, and “mask”includes a reticule having a device pattern which is reduced projectedonto a substrate.

The illuminating optical system IL illuminates the exposure light ELonto the mask M supported by the mask stage MST, and includes a lightsource for exposure, an optical integrator which uniformizes theluminance of a beam emitted from the light source for exposure, acondenser lens which focuses the exposure light EL from the opticalintegrator, a relay lens system, a variable-field aperture which sets aregion on the mask M illuminated by the exposure light EL to a slitshape, and the like. The illuminating optical system IL illuminates apredetermined illumination region on the mask M using the exposure lightEL having an even luminance distribution. Examples of light which can beused as the exposure light EL emitted from the exposure apparatus EX aredeep ultraviolet light (DUV light) such as emission lines (g-line,h-line, and i-line) emitted from a mercury lamp and KrF excimer laserlight (wavelength: 248 nm), and vacuum ultraviolet light (VUV light)from an ArF excimer layer (wavelength: 193 nm), an F₂ laser (wavelength:157 nm), etc. This embodiment uses ArF excimer laser light. As describedabove, the liquid LQ of this embodiment is pure water, which cantransmit even exposure light EL from an ArF excimer laser. Pure wateralso allows transmission of far ultraviolet light (DUV light) such asemission lines (g-line, h-line, and i-line) emitted from a mercury lampand KrF excimer laser light (wavelength: 248 nm).

The mask stage MST can move while holding the mask M, being capable ofmoving two-dimensionally within a plane perpendicular to the opticalaxis AX of the projection optical system PL, i.e., within the X-Y plane,and also minutely rotating in the θZ direction. The mask stage MST isdriven by a mask stage driving device MSTD such as a linear motor. Themask stage driving device MSTD is controlled by the control device CONT.A moving mirror 40 is provided on the mask stage MST. A laserinterferometer 41 is provided facing the moving mirror 40. The laserinterferometer 41 measures the two-dimensional directional position andthe rotation angle of the mask M on the mask stage MST in real time, andoutputs a measurement result to the control device CONT. The controldevice CONT positions the mask M, which is supported by the mask stageMST, by driving the mask stage MST based on the measurement result ofthe laser interferometer 41.

The projection optical system PL uses exposure to project the pattern ofthe mask M onto the substrate P at a predetermined projectionmagnification β, and comprises a plurality of optical elements includingan optical element (lens) 2 provided at a frontal end of the substrate Pside, these optical elements being supported by a lens barrel PK. Inthis embodiment, the projection optical system PL is a reduction systemwith a projection magnification β of, for example, ¼ or ⅕. Theprojection optical system PL may be one of a same-size system or anenlargement system. The projection optical system PL may be one of areflecting system which does not include a refracting element, arefracting system which does not include a reflecting element, and acatadioptric system which includes a refracting element and a reflectingelement.

In this embodiment, the frontal end of the projection optical system PLcan be attached/removed (replaced) with respect to the lens barrel PK.The optical element 2 at the frontal end is exposed from the lens barrelPK, and the liquid LQ in the immersion region AR2 contacts the opticalelement 2. This prevents corrosion and the like of the lens barrel PK,which is made of metal.

The optical element 2 is formed from fluorite. Since fluorite has highaffinity with pure water, the liquid LQ can be made to closely adhere toalmost all of a liquid contact face (end face) 2A of the optical element2. That is, since this embodiment supplies a liquid (water) LQ havinghigh affinity with the liquid contact face 2A of the optical element 2,there is very close adhesion between the liquid LQ and the liquidcontact face 2A of the optical element 2, and the optical element 2 maybe quartz, which has affinity with water. The liquid contact face 2A ofthe optical element 2 may be treated to provide hydrophilic property(liquid affinity) to increase its affinity with the liquid LQ.

The substrate stage PST includes a Z stage 52 which holds the substrateP with the substrate holder PH therebetween, and an XY stage 53 whichsupports the Z stage 52. The XY stage 53 is supported on a base 54. Thesubstrate stage PST is driven by a substrate stage driving device PSTDsuch as a linear motor. The substrate stage driving device PSTD iscontrolled by the control device CONT. The Z stage 52 can move thesubstrate P held by the substrate holder PH in the Z-axis direction andin the θX and θY directions (gradient directions). The XY stage 53 canmove the substrate P held by the substrate holder PH in the XY direction(a direction substantially parallel to the image surface of theprojection optical system PL) and in the θZ direction. The Z stage andthe XY stage can, of course, be provided in a single piece.

A concave 55 is provided on the substrate stage PST, and the substrateholder PH is arranged in the concave 55. A top face 51 of the substratestage PST other than the concave 55 forms a flat face (flat section)which is approximately the same height (same plane) as the surface ofthe substrate P held by the substrate holder PH. In this embodiment, aplate member 50 including the top face 51 is arranged on the substratestage PST such that the plate member 50 can be replaced. Since the topface 51, provided almost in a single plane with the surface of thesubstrate P, is arranged around the substrate P, when immersion-exposingan edge region E of the substrate P, the liquid LQ can be held on theimage surface side of the projection optical system PL and the immersionregion AR2 can be formed satisfactorily. Although there is a gap ofapproximately 0.1 to 2 mm between the edge section of the substrate Pand the plate member 50 which includes the flat face (top face) 51 andis provided around the substrate P, the surface tension of the liquid LQensures that almost none of it wets and spreads into this gap, enablingthe liquid LQ to be held below the projection optical system PL by theplate member 50 when exposing the surrounding area of the substrate P tolight.

Providing that the immersion region AR2 can be formed such that theoptical path space on the image surface side of the projection opticalsystem PL is filled with the liquid LQ, there may acceptably be a slightstep between the surface of the substrate P and the top face 51; forexample in the Z direction, the top face 51 may be lower than thesurface of the substrate P.

A moving mirror 42 is provided on the substrate stage PST (Z stage 52).A laser interferometer 43 is provided facing the moving mirror 42. Thelaser interferometer 43 measures the two-dimensional directionalposition and the rotation angle of the substrate P on the substratestage PST in real time, and outputs a measurement result to the controldevice CONT. Based on the measurement result from the laserinterferometer 43, the control device CONT drives the XY stage 53 viathe substrate stage PST within a two-dimensional coordinate systemstipulated by the laser interferometer 43, and thereby positions thesubstrate P, which is supported by the substrate stage PST, in theZ-axis direction and the Y-axis direction.

The exposure apparatus EX also includes a focus detection system 30which detects face position information of the substrate P surface. Thefocus detection system 30 includes an emitter 30A and a photoreceiver30B, and detects face position information of the substrate P surface byemitting detection light La from the emitter 30A from a diagonaldirection onto the substrate P surface (exposure surface) via the liquidLQ from the emitter 30A and receiving light reflected from the substrateP at the photoreceiver 30B via the liquid LQ. The control device CONTcontrols operations of the focus detection system 30, and, based on thephotoreception result of the photoreceiver 30B, detects the Z-axisdirectional position (focus position) of the substrate P surface withrespect to a predetermined reference face (image surface). Bydetermining focus positions at a plurality of points on the substrate Psurface, the focus detection system 30 can determine the posture of thesubstrate P in a diagonal direction. A system disclosed in, for example,Japanese Unexamined Patent Publication, First Publication No. H8-37149can be used in configuring the focus detection system 30. The focusdetection system 30 may be one which detects the face positioninformation of the substrate P surface without emitting/receiving lightthrough the liquid LQ. In this case, the emission position of thedetection light La of the focus detection system 30 may be set at adistance from the projection region AR1 of the projection optical systemPL.

The control device CONT drives the Z stage 52 of the substrate stage PSTvia the substrate stage driving device PSTD, and thereby controls theZ-axis directional position (focus position) of the substrate P held onthe Z stage 52, and its positions in the θX and θY directions. That is,the Z stage 52 moves based on a command from the control device CONTbased on the detection result of the focus detection system 30, thefocus position (Z position) and gradient angle of the substrate P beingcontrolled such that the surface (exposure surface) of the substrate Pis aligned with the image surface formed via the projection opticalsystem PL and the liquid LQ.

A substrate alignment system 350 is provided near the frontal end of theprojection optical system PL, and detects an alignment mark 1 on thesubstrate P or a substrate side reference mark PFM on a reference member300 provided on the Z stage 52. The substrate alignment system 350 ofthis embodiment utilizes a field image alignment (FIA) method, such asthat disclosed in Japanese Unexamined Patent Publication, FirstPublication No. H4-65603, which holds the substrate stage PST stationarywhile irradiating an illuminating light such as white light from ahalogen lamp onto a mark, uses an image-capturing element to capture animage of the obtain mark within a predetermined image-capturing field,and measures the position of the mark using image processing.

A mask alignment system 360 is provided near the mask stage MST, anddetects a mask side reference mark MFM on the reference member 300provided on the Z stage 52 via the mask M and the projection opticalsystem PL. The mask alignment system 360 of this embodiment utilizes avisual reticule alignment (VRA) method, such as that disclosed inJapanese Unexamined Patent Publication, First Publication No. H7-176468,which illuminates the mark with light, and detects the mark position byimage processing image data of the mark captured by a CCD camera and thelike.

The liquid supply mechanism 10 supplies a predetermined liquid LQ to theimage surface side of the projection optical system PL, and includes aliquid supplier 11 capable of delivering the liquid LQ, and supply pipes13 (13A and 13B) either ends of which are connected to the liquidsupplier 11. The supply pipes 13 have flow passages for allowing theliquid LQ to flow. The liquid supplier 11 includes a tank for storingthe liquid LQ, a pressure pump, and so on. The control device CONTcontrols the liquid supply operation of the liquid supplier 11. Whenforming the immersion region AR2 on the substrate P, the liquid supplymechanism 10 supplies the liquid LQ onto the substrate P.

Note that the tank, the pressure pump, and so on of the liquid supplier11 need not be included in the exposure apparatus EX; instead, it isacceptable to use facilities of a factory or the like where the exposureapparatus EX is installed.

Valves 15A and 15B for opening/closing the flow passages of the supplypipes 13A and 13B are provided midway along the supply pipes 13A and13B, respectively. The opening/closing operations of the valves 15 (15Aand 15B) are controlled by the control device CONT. The valves 15 ofthis embodiment utilize a so-called normal close method, whichmechanically closes the flow passages of the supply pipes 13A and 13Bwhen a drive source (power source) of the exposure apparatus EX (controldevice CONT) stops due to a power failure or the like.

The measuring device 60 which measures time is connected to the valves15 (15A and 15B). The measuring device 60 can detect whether the valves15 have closed the flow passages of the supply pipes 13, and startsmeasuring time when it detects that the control device CONT has closedthe valves 15. The measuring device 60 measures the time elapsed sincethe valves 15 closed the flow passages of the supply pipes 13, i.e., thea time during which the supply of the liquid from the liquid supplymechanism is stopped 10, and outputs the measurement result to thecontrol device CONT. When the measuring device 60 detects that thecontrol device CONT has opened the valves 15, it stops measuring timeand resets the measured time (returns it to zero).

The measuring device 60 can also measure the time elapsed since thevalves 15 open the flow passages of the supply pipes 13, i.e., theliquid supply time of the liquid supply mechanism 10. The measuringdevice 60 outputs this measurement result to the control device CONT.

The liquid collection mechanism 20 collects the liquid LQ from the imagesurface side of the projection optical system PL, and includes a liquidcollector 21 capable of collecting the liquid LQ, and collection pipes23 (23A and 23B) either ends of which are connected to the liquidcollector 21. The liquid collector 21 utilizes a vacuum system (suctiondevice) such as a vacuum pump, an air-liquid separator which separatesthe collected liquid LQ from the air, a tank for containing thecollected liquid LQ, and so on. Instead of fitting the exposureapparatus EX with a vacuum pump, a vacuum system of a factory where theexposure apparatus EX is installed may be used as the vacuum system. Theliquid collection operation of the liquid collector 21 is controlled bythe control device CONT. To form the immersion region AR2 on thesubstrate P, the liquid collection mechanism 20 collects a predeterminedamount of the liquid LQ on the substrate P supplied by the liquid supplymechanism 10.

Note that the vacuum system, the air-liquid separator, tank, and thelike of the liquid collector 21 need not be included in the exposureapparatus EX; instead, it is possible to use equipment at a factory orthe like where the exposure apparatus EX is installed.

Among the plurality of optical elements which form the projectionoptical system PL, a flow passage formation member 70 is arranged nearthe optical element 2 which contacts the liquid LQ. The flow passageformation member 70 is a ring-shaped member provided above the substrateP (substrate stage PST) such as to enclose the side faces of the opticalelement 2. A gap is provided between the flow passage formation member70 and the optical element 2, and the flow passage formation member 70is supported by a predetermined support mechanism such that it isseparated vibrationally from the optical element 2.

The flow passage formation member 70 can be formed from aluminum,titanium, stainless steel, duralumin, or an alloy of these.Alternatively, the flow passage formation member 70 may be constructedfrom a light-transmitting transparent member (optical member) such asglass (quartz).

The flow passage formation member 70 includes liquid supply openings 12(12A and 12B) which are provided above the substrate P (substrate stagePST) and face the substrate P surface. In this embodiment, the flowpassage formation member 70 includes two liquid supply openings 12A and12B. The liquid supply openings 12A and 12B are provided in a bottomface 70A of the flow passage formation member 70.

The flow passage formation member 70 contains supply flow passages whichcorrespond to the liquid supply openings 12A and 12B. A plurality of(two) supply pipes 13A and 13B are provided in correspondence with theliquid supply openings 12A and 12B and the supply flow passages. One endof each supply flow passage connects to the liquid supplier 11 via thesupply pipes 13A and 13B, and another end of each connects to the liquidsupply openings 12A and 12B.

Flow meters 16 (16A and 16B) are provided midway along each of thesupply pipes 13A and 13B, and measure the amount of flow per unit oftime of the liquid LQ which is supplied from the liquid supplier 11 andflows along the supply pipes 13A and 13B. Measurement results from theflow meters 16A and 16B are output to the control device CONT.

Based on the measurement results of the flow gauges 16, the controldevice CONT can determine whether the liquid supply mechanism 10 issupplying liquid along the supply pipes 13. That is, when the controldevice CONT determines, based on the measurement results of the flowmeters 16, that the liquid LQ is not flowing along the flow passages ofthe supply pipes 13, it can determine that the supply of the liquid fromthe liquid supply mechanism 10 has stopped. On the other hand, when thecontrol device CONT determines, based on the measurement results of theflow gauges 16, that the liquid LQ is flowing along the flow passages ofthe supply pipes 13, it determines that the liquid supply mechanism 10is supplying liquid.

Flow control devices known as mass flow controllers (not shown) areprovided midway along the supply pipes 13A and 13B, and controls theamounts per unit of time of liquid supplied from the liquid supplier 11along the liquid supply openings 12A and 12B. These flow ratecontrollers control the amount of liquid supplied in compliance withcommand signals from the control device CONT.

The flow passage formation member 70 also includes liquid collectionopenings 22 (22A and 22B) which are provided above the substrate P(substrate stage PST) and arranged facing the substrate P surface. Inthis embodiment, the flow passage formation member 70 has two liquidcollection openings 22A and 22B. The liquid collection openings 22A and22B are provided in the bottom face 70A of the flow passage formationmember 70.

The flow passage formation member 70 also includes collection flowpassages corresponding to the liquid collection openings 22A and 22B. Aplurality of (two) collection pipes 23A and 23B are provided such as tocorrespond to the liquid collection openings 22A and 22B and thecollection flow passages. One end of each supply flow passage connectsto the liquid collector 21 via the collection pipes 23A and 23B, andanother end of each connects to the liquid collection openings 22A and22B.

In this embodiment, the flow passage formation member 70 forms one partof each of the liquid supply mechanism 10 and the liquid collectionmechanism 20. The liquid supply openings 12A and 12B which form theliquid supply mechanism 10 are arranged on respective sides of the Xaxis direction with the projection region AR1 of the projection opticalsystem PL between them, and the liquid collection openings 22A and 22Bwhich form the liquid collection mechanism 20 are provided on outersides of the liquid supply openings 12A and 12B of the liquid supplymechanism 10 with respect to the projection region AR1 of the projectionoptical system PL. In this embodiment, the projection region AR1 of theprojection optical system PL is set to a rectangular shape in plan viewwith its longitudinal direction in the Y-axis direction and its shortdirection in the X-axis direction.

The control device CONT controls the operations of the liquid supplier11 and the flow rate controllers. When supplying the liquid LQ onto thesubstrate P, the control device CONT delivers the liquid LQ from theliquid supplier 11, and supplies it via the supply pipes 13A and 13B,and the supply flow passages, onto the substrate P from the liquidsupply openings 12A and 12B provided above the substrate P. At thistime, the liquid supply openings 12A and 12B are arranged on respectivesides of the projection region AR1 of the projection optical system PL,enabling the liquid LQ to be supplied from both sides of the projectionregion AR1 via the liquid supply openings 12A and 12B. The amounts ofthe liquid LQ that are supplied from the liquid supply openings 12A and12B onto the substrate P per unit of time can be individually controlledby the flow rate controllers which are respectively provided along thesupply pipes 13A and 13B.

The control device CONT controls the liquid collection operation of theliquid collector 21. The control device CONT can control the amount ofliquid collected by the liquid collector 21 amount per unit of time. Theliquid LQ on the substrate P collected from the liquid collectionopenings 22A and 22B provided above the substrate P is collected to theliquid collector 21 via the flow passages of the flow passage formationmember 70 and via the collection pipes 23A and 23B.

While in this embodiment, the supply pipes 13A and 13B are connected toone liquid supplier 11, a plurality of liquid suppliers 11 (two in thiscase) may be provided in correspondence with the number of supply pipes,and the supply pipes 13A and 13B may be respectively connected to theplurality of liquid suppliers 11. While the collection pipes 23A and 23Bare connected to one liquid collector 21, a plurality of liquidcollectors 21 (two in this case) may be provided in correspondence withthe number of collection pipes, and the collection pipes 23A and 23B maybe respectively connected to the plurality of liquid collectors 21.

The mechanism for forming the immersion region AR2 locally on thesubstrate P (substrate stage PST) is not limited to that describedabove, it being possible to us a mechanism such as that disclosed in USPatent Application No. 2004/020782, and the some of the contents of thedocument is herein incorporated in this text, within the limitspermitted by national regulations of countries designated or elected inthis international application.

The liquid contact face 2A of the optical element 2 of the projectionoptical system PL and the bottom face (liquid contact face) 70A of theflow passage formation member 70 have hydrophilic property (affinitywith liquid). In this embodiment, the liquid contact faces of theoptical element 2 and the flow passage formation member 70 are impartedliquid affinity, thereby giving them hydrophilic property. In otherwords, hydrophilic property is given to the liquid contact faces ofsurfaces of at least the members which are opposite the exposed face(surface) of the substrate P held by the substrate stage PST. Since theliquid LQ of this embodiment is water with high polarity, the liquidaffinity (hydrophilic) treatment may include, for example, forming athin film of a substance with a highly polar molecular structure such asalcohol and thereby imparting hydrophilic property to the liquid contactfaces of the optical element 2 and the flow passage formation member 70.That is, when using water as the liquid LQ, a thin film with a highlypolar molecular structure, such as an OH group, is preferably providedon the liquid contact faces. Alternatively, a hydrophilic material suchas MgF₂, Al₂O₃, and SiO₂ may be provided on the liquid contact faces.

The bottom face (the face which faces the substrate P side) 70A of theflow passage formation member 70 is almost flat, and the bottom face(liquid contact face) 2A of the optical element 2 is also flat, thebottom face 70A of the flow passage formation member 70 and the bottomface 2A of the optical element 2 being arranged approximately in asingle plane. This enables the immersion region AR2 to be satisfactorilyformed over a wide range.

The bottom face 70A of the flow passage formation member 70 and thebottom face 2A of the optical element 2 need not be arranged in a singleplace, and there may acceptably be a step between the bottom face 70A ofthe flow passage formation member 70 and the bottom face 2A of theoptical element 2. For example, the bottom face 2A of the opticalelement 2 may deviate from the bottom face 70A of the flow passageformation member 70 toward the +Z direction side.

The top face 51 of the substrate stage PST is a flat face (flatsection), and is given water-repellant property by water-repellanttreatment. For example, this water-repellant treatment of the top face51 may be performed by applying a water-repellant material such as afluororesin material or an acrylic resin material, or by coating athin-film of the water-repellant material. A material which is insolublewith respect to the liquid LQ is used as the material for obtainingwater-repellant. All or part of the substrate stage PST may be formedfrom a water-repellant material, including among others a fluororesinsuch as polytetrafluoroethylene (Teflon®). The plate member 50, whichincludes the top face 51 of the substrate stage PST, may also be formedfrom a water-repellant material such as polytetrafluoroethylene.

The reference member 300 is arranged on the substrate stage PST at apredetermined position on the outer side of the substrate P. Thesubstrate side reference mark PFM, which the substrate alignment system350 detects not through liquid, and the reference mark MFM, which themask alignment system 360 detects through the liquid, are provided onthe reference member 300 in a predetermined positional relationship.Atop face 301A of the reference member 300 is almost a flat face (flatsection), and is arranged at approximately the same height as (in singleplane with) the substrate P surface held on the substrate stage PST andthe top face 51 of the substrate stage PST. The top face 301A of thereference member 300 can also function as a reference face of the focusdetection system 30. The substrate alignment system 350 detects analignment mark 1 formed on the substrate P.

Although not shown in the figure, a luminance unevenness sensor such asthat disclosed in Japanese Unexamined Patent Publication, FirstPublication No. S57-117238 is provided as a sensor for measurement onthe substrate stage PST at a predetermined position on the outer side ofthe substrate P. The luminance unevenness sensor includes a top platehaving a flat face (flat section) provided at almost the same height as(within a single plane with) the surface of the substrate P held by thesubstrate stage PST and the top face 51 of the substrate stage PST. Alight-receiving element (detector) which forms the luminance unevennesssensor is buried in the substrate stage PST (below the top plate), andreceives the exposure light via the liquid on the top plate. Similarly,an aerial image-measuring sensor such as that disclosed in JapaneseUnexamined Patent Publication, First Publication No. 2002-14005 isprovided as a sensor for measurement on the substrate stage PST at apredetermined position on the outer side of the substrate P. The aerialimage-measuring sensor includes a top plate having a flat face (flatsection) provided at almost the same height as (within a single planewith) the surface of the substrate P held by the substrate stage PST andthe top face 51 of the substrate stage PST. An irradiance level sensor(luminance sensor) such as that disclosed in Japanese Unexamined PatentPublication, First Publication No. H11-16816 is provided on thesubstrate stage PST, with a top plate of the irradiance level sensorarranged at almost the same height as (in a single plane with) thesurface of the substrate P held by the substrate stage PST and the topface 51 of the substrate stage PST. Each of the sensors for measurementdescribed above obtains measurements by receiving light through theliquid above its top plate.

Subsequently, a method of exposing a pattern of a mask M onto thesubstrate P using the exposure apparatus EX of the above configurationwill be explained.

It is assumed here that, before starting exposure of the substrate P,the positional relationship between detection reference positions of thesubstrate alignment system 350 and projection positions of the patternimage of the mask M has already been measured using the substratealignment system 350, the mask alignment system 360, the referencemember 300, etc.

It is also assumed that the various types of sensors mounted on thesubstrate stage PST have finished measuring, and that adjustments suchas correction have been made based on these measurement results.

Firstly, as shown in FIG. 2, the substrate P which is the target ofexposure processing is loaded onto the substrate stage PST by a loadingsystem (loading device) H. Upon loading the substrate P onto thesubstrate stage PST, the substrate stage PST is moved to a load positionaway from the projection optical system PL. At the load position, thesubstrate P is loaded onto the substrate stage PST by the loading systemH.

When the substrate stage PST is at the load position, the control deviceCONT closes the flow passages of the supply pipes 13 by driving thevalves 15, and stops the supply of the liquid from the liquid supplymechanism 10. As described above, the a time during which the supply ofthe liquid from the liquid supply mechanism is stopped 10 is monitoredby the measuring device 60.

In order to perform alignment exposure on the substrate P, the controldevice CONT uses the substrate alignment system 350 to measure alignmentmarks 1 which are formed in accompaniment in each of a plurality of shotregions on the substrate P. While the substrate alignment system 350 ismeasuring the alignment marks 1, the laser interferometer 43 measuresthe position of the substrate stage PST. The control device CONTmeasures the alignment marks 1 while the immersion regions for theliquid LQ are not formed on the substrate P (non-immersed state). Whilemeasuring the alignment marks 1, the control device CONT closes the flowpassages of the supply pipes 13 of the liquid supply mechanism 10 bydriving the valves 15, and stops the supply of the liquid from theliquid supply mechanism 10, whereby the measuring device 60 continues tomeasure the liquid supply stopping time.

Based on the detection result of the alignment marks 1, the controldevice CONT determines positional information of the shot regions withrespect to the detection reference positions of the substrate alignmentsystem 350, and moves the substrate stage PST based on the positionalinformation and a base line amount measured earlier, thereby aligningthe projection positions of the pattern image of the mask M with theshot regions.

When exposure of the shot regions of the substrate P starts, the controldevice CONT opens the flow passages of the supply pipes 13 by drivingthe valves 15, and allows the liquid supply mechanism 10 to supplyliquid. The measuring device 60 detects that the flow passages of thesupply pipes 13 have opened, stops measuring the liquid supply stoppingtime, and resets the measuring time (returns it to zero). In parallelwith the supply of the liquid LQ by the liquid supply mechanism 10 ontothe substrate P, the control device CONT makes the liquid collectionmechanism 20 collect the liquid LQ and moves the substrate stage PSTsupporting the substrate P in the X-axis direction (scanning direction)while projecting a pattern image of the mask M onto the substrate P viathe liquid LQ between the projection optical system PL and the substrateP and via the projection optical system PL.

The liquid LQ which is supplied from the liquid supplier 11 of theliquid supply mechanism 10 in order to form the immersion region AR2flows along the supply pipes 13A and 13B, and is then supplied via thesupply flow passages formed in the flow passage formation member 70 ontothe substrate P from the liquid supply openings 12A and 12B. The liquidLQ supplied onto the substrate P from the liquid supply openings 12A and12B is supplied such that it wets and spreads between the bottom endface of the frontal end (optical element 2) of the projection opticalsystem PL and the substrate P, whereby the immersion region AR2, whichis smaller than the substrate P and larger than the projection regionAR1, is locally formed a part of the substrate P which includes theprojection region AR1. At this time in the liquid supply mechanism 10,the control device CONT simultaneously supplies the liquid LQ from eachof the liquid supply openings 12A and 12B, arranged on both sides of theX-axis direction (scanning direction) of the projection region AR1, ontothe substrate P from both sides of the projection region AR1 in relationto the scanning direction. This forms the immersion region AR2 evenlyand satisfactorily.

The exposure apparatus EX of this embodiment projects the pattern imageof the mask M onto the substrate P while moving the mask M and thesubstrate P in the X-axis direction (scanning direction); duringscanning exposure, a pattern image of part of the mask M is projectedinto the projection region AR1 via the liquid LQ in the immersion regionAR2 and the projection optical system PL, and, in synchronism with themotion of the mask M in the −X direction (or the +X direction) atvelocity V, the substrate P moves in the +X direction (or the −Xdirection) with respect to the projection region AR1 at a velocity β·V(β being the projection magnification). A plurality of shot regions areset on the substrate P, and, after completing exposure to one shotregion, a stepping motion of the substrate P moves the next shot regionis moved to the scanning start position, and this step-and-scan methodis thereafter performed sequentially in each shot region while movingthe substrate P.

After immersion exposure of the substrate P ends, the control deviceCONT closes the flow passages of the supply pipes 13 by driving thevalves 15, and stops the supply of the liquid from the liquid supplymechanism 10. The measuring device 60 detects the fact that the flowpassages of the supply pipes 13 have been closed by the valves 15, andusing that time as a reference, starts measuring the time that the flowpassages of the supply pipes 13 are closed, i.e., the a time duringwhich the supply of the liquid from the liquid supply mechanism isstopped 10. The measuring device 60 outputs a measurement result of thestopping time to the control device CONT.

After stopping the supply of the liquid from the liquid supply mechanism10, the control device CONT continues driving the liquid collectionmechanism 20 for a predetermined period of time, and collects the liquidLQ which remains on the exposed substrate P and on the substrate stagePST holding the substrate P. While the liquid collection mechanism 20 iscollecting the liquid LQ, the substrate stage PST may move in the XYdirection with respect to the liquid collection openings 22. Thisenables the remaining liquid LQ to be collected over a wide range on thesubstrate P and the substrate stage PST.

After the liquid supply mechanism 10 stops supplying liquid and theoperation of collecting liquid from the substrate P and the substratestage PST ends, the control device CONT moves the substrate stage PST toan unload position away from the projection optical system PL. At theunload position, the exposed substrate P on the substrate stage PST isunloaded by an unloading system (unloading device).

As described above, during loading and unloading of the substrate P, andduring measuring processes and the like performed by the substratealignment system 350 in the non-immersed state, the measuring device 60measures (monitors) the liquid supply stopping time of the liquid supplymechanism 10.

As the liquid supply stopping time of the liquid supply mechanism 10(the time from the start of stopping liquid supply of the liquid supplymechanism 10 until restarting liquid supply) increases, the liquid LQremaining in the supply pipes 13 becomes stagnant and the cleanlinessdecreases. When this liquid of reduced cleanliness is supplied onto thesubstrate P or onto the substrate stage PST (including the referencemember 300 and the sensors for measuring) during subsequent exposure andmeasuring processes of the substrate P, the inside of the supply pipes13, the substrate P, and members on the substrate stage PST may becomecontaminated and the exposure precision and the measuring precision maydeteriorate.

Accordingly, the control device CONT compares the stopping time measuredby the measuring device 60 with a predetermined allowable time, and,when the liquid supply stopping time exceeds the predetermined allowabletime, the control device CONT restarts the supply of the liquid from theliquid supply mechanism 10. For example, if a problem occurs whenunloading the substrate P, and the substrate P whose exposure iscomplete continues to be held on the substrate stage PST, there is apossibility that the liquid supply stopping time will exceed thepredetermined allowable time. When the liquid supply stopping timeexceeds the predetermined allowable time in this way, the control deviceCONT restarts the supply of the liquid from the liquid supply mechanism10. Consequently, the liquid LQ remaining in the supply pipes 13 can beflushed out and prevented from remaining in them. This prevents theproblems caused by reduced cleanliness of the liquid LQ in the supplypipes 13.

The allowable time (i.e., the allowable time from starting stopping ofthe supply of the liquid from the liquid supply mechanism 10 untilrestarting the liquid supply) can be set based on a time at which thecleanliness of liquid LQ remaining in the supply pipes 13 does notdecrease below a permissible level. Information relating to thisallowable time is determined beforehand by tests, simulations, and soon, and is stored in the storage device MRY.

For example, if the liquid LQ is left to accumulate in the supply pipes13 for a long period of time as described above, fungi such as bacteriaproliferate in the supply pipes 13 and near the liquid supply openings12, reducing the cleanliness of the liquid LQ. Preferably therefore, theallowable time is determined taking into a consideration theproliferation time of bacteria in the flow passages of the supply pipes13. In the case, a allowable time T_(B) can be determined beforehand bytests and simulations, and stored in the storage device MRY. When the atime during which the supply of the liquid from the liquid supplymechanism is stopped 10 exceeds the allowable time T_(B), which isdetermined taking into a consideration the proliferation time ofbacteria, supply of liquid from the liquid supply mechanism 10 restarts,making it possible to prevent generation (proliferation) of bacteria inthe supply pipes 13 and near the liquid supply openings 12.

During immersion exposure of the substrate P, the exposure light EL isirradiated onto the substrate P with the bottom face 2A of theprojection optical system PL contacting the liquid LQ (immersed state);when this immersion exposure of the substrate P ends, after reverting tothe non-immersed state by performing a collection operation of theliquid LQ, if the liquid LQ is allowed to stick to (remain on) thebottom face 2A of the projection optical system PL for a long period oftime, the liquid LQ may dry and form marks of remaining liquid(hereinafter ‘watermarks’) on the bottom face 2A of the projectionoptical system PL, leading to problems such as those caused by foreignparticles sticking to the watermarks. Watermarks are thought to becaused when the liquid LQ stuck to the bottom face 2A dries aftersurrounding impurities merge into it. On the other hand, it is thoughtthat watermarks can be suppressed and removed by moistening the bottomface 2A with the liquid LQ. Therefore, the allowable time may bedetermined taking into a consideration the drying time of the liquid LQstuck to the bottom face 2A of the projection optical system PL.Alternatively, it may be determined such that impurities do not stick tothe bottom face 2A due to drying of the liquid LQ sticking to the bottomface 2A of the projection optical system PL. A allowable time T_(WM)relating to watermark formation can be determined beforehand by testsand simulations, and stored in the storage device MRY. The controldevice CONT uses the measuring device 60 to measure the time elapsingfrom the immersed state of the bottom face 2A of the projection opticalsystem PL until its non-immersed state, and, when this elapsed time(i.e., the a time during which the supply of the liquid from the liquidsupply mechanism is stopped 10) exceeds the allowable time T_(WM),restarts the supply of the liquid from the liquid supply mechanism 10such that the bottom face 2A of the projection optical system PLcontacts the liquid LQ (such as to be moistened by the liquid LQ),thereby preventing the generation of watermarks.

When the time elapsed from shifting from the immersed state to thenon-immersed state exceeds the allowable time T_(WM), and the supply ofthe liquid from the liquid supply mechanism 10 restarts, the projectionoptical system PL and the flat face on the substrate stage PST arealigned facing each other, as shown in FIG. 3, before restarting thesupply of the liquid from the liquid supply mechanism 10. That is, whenthe a time during which the supply of the liquid from the liquid supplymechanism is stopped 10 exceeds the predetermined allowable time, thecontrol device CONT determines, based on the measurement result of thelaser interferometer 43, whether the projection optical system PL andthe flat face on the substrate stage PST are facing each other, and,when it determines that the projection optical system PL and the flatface on the substrate stage PST are facing each other, restarts thesupply of the liquid from the liquid supply mechanism 10. This enablesthe bottom face 2A of the projection optical system PL to be moistenedby the liquid LQ. The flat face on the projection optical system in thiscase includes the top face 51 of the substrate stage PST, the substrateP surface held by the substrate stage PST, the reference member 300, andthe top plates of the sensors for measuring (the luminance unevennesssensor, the aerial image-measuring sensor, etc.). When the controldevice CONT determines that the projection optical system PL and theflat face on the substrate stage PST are not facing each other, it movesthe substrate stage PST based on the measurement result of the laserinterferometer 43 such that the projection optical system PL and theflat face of the substrate stage PST are facing each other, and thenstarts the supply of the liquid from the liquid supply mechanism 10. Thesubstrate P is preferably held on the substrate stage PST when startingthe supply of the liquid from the liquid supply mechanism 10.

As described above, after measuring in the immersed state, where theliquid LQ is arranged on the reference member 300 and on the top platesof the sensors for measuring, and then shifting to the non-immersedstate, there is a possibility that watermarks will form on the referencemember 300 and on the top plates of the sensors for measuring, or thetop face 51 of the substrate stage PST, and the like. Accordingly, whenmoistening the bottom face 2A of the projection optical system PL, theliquid LQ is supplied from the liquid supply mechanism 10 with theprojection optical system PL facing the reference member 300 (or the topplates of the sensors for measuring), thereby preventing watermarks fromforming on the bottom face 2A of the projection optical system PL andpreventing the problem of watermarks forming on the reference member 300and the like.

When T_(B) is the allowable time determined taking into a considerationthe proliferation time of bacteria, T_(WM) is the allowable time whichis determined taking into a consideration the watermark formation time,and T is the a time during which the supply of the liquid from theliquid supply mechanism is stopped 10 (the time lapse between theimmersed state and the non-immersed state), liquid supply may berestarted when T=min (T_(B), T_(WM)).

The allowable time is not limited only to T_(B) and T_(WM) mentionedabove, and may be determined beforehand also with regard to thereference member 300, the top plates, the top face 51, and so on, thereference member 300 and so on being moistened with the liquid LQ whenthe time lapse from their immersed state to their non-immersed stateexceeds the allowable time. By preventing formation of watermarks on thereference member 300, the top plates, and so on in this manner, it ispossible to prevent deterioration in the measuring precision of thesensors which use the reference member 300 and the top plates.

In one conceivable configuration of the focus detection system 30,predetermined optical members among the plurality of optical memberswhich form the optical system of the focus detection system 30 may bemade to contact the immersion region AR2. Therefore, the allowable timemay be determined in order to prevent formation of watermarks on theseoptical members, the supply of the liquid from the liquid supplymechanism 10 being restarted when the allowable time is exceeded. Thiscan maintain the detection precision of the focus detection system 30.

After loading the substrate P onto the substrate stage PST, during theseries of processes of immersion-exposing the substrate P and unloadingit from the substrate stage PST, the supply of the liquid from theliquid supply mechanism 10 may be restarted when the liquid supplystopping time exceeds the allowable time. For example, if the allowabletime T_(B) (or T_(WM)) is exceeded during measuring of the substrateside reference marks PFM on the reference member 300 or the alignmentmarks 1 on the substrate P while the liquid supply is stopped and thesubstrate alignment system 350 is in the non-immersed state, themeasuring operation of the substrate alignment system 350 is temporarilyhalted, a flat face on a different substrate stage PST from that of thereference member 300 is aligned facing the bottom face 2A of theprojection optical system PL, and liquid supply restarts. Aftermoistening the bottom face 2A of the projection optical system PL, theliquid collection mechanism 20 collects the liquid LQ and the measuringoperation of the substrate alignment system 350 may be restarted.

While the embodiment describes an example of a series of processesperformed after loading the substrate P onto the substrate stage PST,whereby the substrate P is immersion-exposed and unloaded from thesubstrate stage PST, the liquid supply can of course be restarted duringmaintenance of the exposure apparatus EX or during manual assistance.That is, a situation where the supply of the liquid from the liquidsupply mechanism 10 must be stopped can arise not only duringreplacement of the substrate P, but also during maintenance and the likeof the exposure apparatus EX such as when replacing components. In suchcases, the a time during which the supply of the liquid from the liquidsupply mechanism is stopped 10 is measured by the measuring device 60,and an appropriate procedure can be performed based on the measurementresult. For example, when the substrate P is exceeded while the supplyof the liquid from the liquid supply mechanism 10 is stopped duringmaintenance of the exposure apparatus EX, the substrate stage PST may bemoved such that it faces the bottom face 2A of the projection opticalsystem PL, and the supply of liquid is then restarted. As anotherexample, when the substrate P which is the target of exposure processingis not being held on the substrate stage PST (the substrate holder PH)due to maintenance, a loading error, or the like, it is acceptable toplace a dummy substrate on the substrate stage PST, move the substratestage PST below the projection optical system PL, and then restart theliquid supply. By restarting the liquid supply while the substrateholder PH is holding the substrate P or a dummy substrate in thismanner, it is possible to prevent problems of leaking current and rustcaused by the liquid LQ wetting and spreading into the concave 55 of thesubstrate stage PST and the like.

As described above, the a time during which the supply of the liquidfrom the liquid supply mechanism is stopped 10 is measured using themeasuring device 60, and, based on the measurement result, anappropriate procedure, such as a flushing operation of restarting thesupply of the liquid LQ before it stagnates and cleanliness decreases,can be performed, thereby preventing the problem of supplying liquid LQof reduced cleanliness onto the substrate P, the reference member 300which functions as a measuring member, and the top plates of the sensorsfor measuring. Based on the measurement result of the measuring device60, it is also possible to perform an appropriate procedure, such asmoistening the bottom face 2A of the projection optical system PL andthe top of the reference member 300 with the liquid LQ, beforewatermarks are formed. Therefore, the problem of watermarks forming onthe bottom face 2A of the projection optical system PL and the like canbe prevented. Thus, even if there is a possibility of problems arisingdue to stopping of the supply of the liquid from the liquid supplymechanism 10, an appropriate procedure can be performed based on themeasurement result of the measuring device 60, whereby generation ofproblems can be prevented.

While one conceivable method of preventing generation of bacteria andthe like is to add an additive such as an anticorrosive to the liquidLQ, when using pure water as the liquid LQ as in this embodiment, it ispreferable not to add an additive since it will change the materialcharacteristics of the liquid LQ. Therefore, by flushing (cleaning) thesupply pipes 13 by restarting the supply of liquid as in the invention,generation of bacteria can be prevented without altering the materialcharacteristics of the liquid LQ to deal with bacteria.

The liquid LQ, which is supplied from the liquid supply mechanism 10 inorder to clean the supply pipes 13 and as a countermeasure againstwatermarks on the bottom face 2A, may be collected by another collectionmechanism instead of the liquid collection mechanism 20. On the otherhand, since there is a possibility that bacteria will be generated inthe liquid collection openings 22 and the collection pipes 23 of theliquid collection mechanism 20, they can be cleaned by liquid collectionusing the liquid collection mechanism 20.

As described above, when starting the liquid supply, the substrate stagePST is moved such that it faces the bottom face 2A of the projectionoptical system PL; here, the fact that the substrate stage PST has movedand the fact that the liquid supply has restarted may be reported usinga predetermined warning device. This enables an operator, who isperforming an operation in the exposure apparatus EX during maintenanceor the like, to be informed that the substrate stage PST has moved andthat the liquid supply has restarted. Means such as a warning sound, awarning light, or a display, can be used as the warning device.

If the time measured by the measuring device 60 exceeds thepredetermined allowable time, the predetermined warning device need onlynotify the operator of this fact. This enables the operator to executecontrol to restart the supply of the liquid from the liquid supplymechanism 10.

When restarting the liquid supply, instead of a configuration where thebottom face 2A of the projection optical system PL is facing thesubstrate stage PST, a member (device) other than the substrate stagePST including a flat face may be arranged facing the bottom face 2A ofthe projection optical system PL.

For example, when a stage for measurement is provided separate from thesubstrate stage PST as disclosed in Japanese Unexamined PatentPublication, First Publication No. H11-135400, the supply of the liquidfrom the liquid supply mechanism 10 may be started with the sensor formeasurement facing the projection optical system PL.

Preferably in such cases, the control device CONT starts the supply ofthe liquid from the liquid supply mechanism 10 after determining whetherthe other member such as the stage for measurement is facing theprojection optical system PL.

When performing the plurality of processes described above (loading,measuring, and exposing) sequentially, a sequence for performing themmay be set such that the allowable time is not exceeded. For example,although the possibility that the liquid supply stopping time willexceed the allowable time increases if the substrate alignment system350 measures the substrate side reference marks PFM and then continuesby measuring the alignment marks 1 on the substrate P in thenon-immersed state, this possibility can be reduced by, for example,alternating the processes performed in the non-immersed state with thoseperformed in the immersed state, such as measuring of mask sidereference mark MFM by the mask alignment system 360 and measuring usingthe luminance unevenness sensor. When sequentially performing aplurality of processes in the non-immersed state and the immersed statebased on the allowable time in this way, the sequence of the pluralityof processes may be set based on the allowable time.

While in the embodiment described above, the measuring device 60 detectswhether the valves 15 have closed the flow passages of the supply pipes13, it is acceptable if the measuring device 60 is incorporated in thecontrol device CONT and starts measuring time when the control deviceCONT controls the valves 15 such as to close the flow passages of thesupply pipes 13.

While in the embodiment described above, the stop of the supply of theliquid from the liquid supply mechanism 10 is determined from theoperation of the valves 15, it can also be determined based on themeasurement results of the flow meters 16 as mentioned above. Therefore,when the supply of the liquid from the liquid supply mechanism 10 stops,the control device CONT may start measuring time using the measuringdevice 60, based on the measurement results of the flow meters 16.

It is also acceptable for the measuring device 60 to start measuringtime using as a reference the point where the amount of flow measured bythe flow meters 16 provided in the supply pipes 13 drops below apredetermined amount.

Since flow meters can also be provided in the collection pipes 23 tomonitor the amount of flow in them, making it possible to detect thatthe supply of the liquid from the liquid supply mechanism 10 has stoppedand that the bottom face 2A of the projection optical system PL hasreached the non-immersed state, the measuring device 60 may startmeasuring time using as a reference the point where the amount of flowmeasured by the flow meters provided in the collection pipes 23 dropsbelow a predetermined amount.

It is also acceptable to mount a sensor which detects theexistence/nonexistence of liquid on the image surface side of theoptical element 2 of the projection optical system PL, and make themeasuring device 60 start measuring time using the fact that the sensordetects no water as a reference. For example, the focus detection system30 may be used as this sensor. The detection light (reflected light) ofthe focus detection system 30 passes the image surface side of theprojection optical system PL, and, since a detection error is generatedin the focus detection system 30 when there is no more liquid LQ on theimage surface side of the projection optical system PL, i.e., on theoptical path of the detection light (reflected light), theexistence/nonexistence of liquid on the image surface side of theoptical element 2 of the projection optical system PL can be confirmedby monitoring this detection error.

As described above, a plurality of mechanisms may be provided in orderto detect the stop of the supply of the liquid from the liquid supplymechanism 10, and the non-immersed state of the bottom face 2A of theoptical element 2 of the projection optical system PL, and thesemechanisms may be combined as appropriate before the measuring device 60starts measuring time.

When there is a possibility that the stopping time of liquid supply fromthe liquid supply mechanism 10 during maintenance or the like of theexposure apparatus EX may exceed the allowable time, it is acceptable ifthe supply of the liquid from the liquid supply mechanism 10 and theliquid collection performed by the liquid collection mechanism 20 arecontinued for a predetermined time, and clean liquid LQ is used to cleanthe liquid contact faces such as bottom face 2A of the optical element 2of the projection optical system PL, the bottom face 70A of the flowpathformation member 70, and the top face 51 of the substrate stage PST,before stopping the supply of the liquid from the liquid supplymechanism 10. Consequently, even if the liquid LQ remains on the bottomface 2A of the projection optical system PL and the like, sinceimpurities and pollutant contained in the liquid LQ can be reduced, theformation of marks such as watermarks can be suppressed.

Furthermore in the embodiment described above, problems caused by a longa time during which the supply of the liquid from the liquid supplymechanism is stopped 10 are prevented by restarting the supply of theliquid from the liquid supply mechanism 10 when the stopping timeexceeds a predetermined allowable time. However, there are cases where,even though the predetermined substrate P elapses, the liquid supplycannot start due to repair of various errors and maintenance. In suchcases, it is acceptable to continue measuring the stopping time of theliquid supply and, based on the result, replace the supply pipes 13, theoptical element 2, and the like.

While the embodiment described above measures the stopping time of theliquid supply to the emission side (image surface side) of the opticalelement 2 of the projection optical system PL, when the optical pathspace on the incident side of the immersion region AR2 of the projectionoptical system PL is filled with liquid (pure water), as disclosed inInternational Publication No. 2004/019128, it is acceptable to measurethe stopping time of the liquid supply to the incident side of theoptical element 2, or the time from the moment when the incident side ofthe optical element 2 switches from an immersed state to a non-immersedstate

While in the embodiment described above, the time of the non-immersedstate of the bottom face 2A of the optical element 2 of the projectionoptical system PL mounted on the exposure apparatus EX can be measuredby measuring the a time during which the supply of the liquid from theliquid supply mechanism is stopped 10, as for example disclosed inInternational Publication No. 2004/05729, various measurements can alsobe made by during adjustment steps and the like prior to mounting theprojection optical system PL in the exposure apparatus EX, by immersingthe bottom face 2A of the projection optical system PL in liquid.Preferably in such cases, the time from the immersed state of the bottomface 2A of the projection optical system PL to its non-immersed state ismeasured, and the bottom face 2A is immersed in the liquid if, forexample, this time exceeds a predetermined allowable time.

As described above, the liquid LQ in this embodiment is pure water. Purewater has advantages of being easy to obtain in large quantities atsemiconductor manufacturing factories and the like, and of not affectingthe photoresist on the substrate P, optical elements (lenses) and thelike. Since pure water does not affect the environment and containsremarkably few impurities, it may also be expected to clean the surfaceof the substrate P and the surfaces of optical elements provided on thefront end face of the projection optical system PL. When pure watersupplied from a factory or the like has a low level of purity, theexposure apparatus EX may be provided with an ultra-pure watermanufacturing apparatus.

The refractive index n of pure water (water) with respect to theexposure light EL with a wavelength of approximately 193 nm is said tobe about 1.44, and, when using an ArF excimer laser (wavelength 193 nm)as the source for the exposure light EL, the wavelength is shortened to1/n (i.e., approximately 134 nm), obtaining a high-resolution image onthe substrate P. Since the depth of field is enlarged approximately ntimes (i.e., approximately 1.44 times) in comparison with transmissionthrough air, when the depth of field need only be approximately the sameas that in air, the numerical aperture of the projection optical systemPL can be increased, further enhancing the resolution.

When using the immersion method described above, the numerical apertureNA of the projection optical system may rise to between 0.9 and 1.3.When the numerical aperture of the projection optical system increasesin this way, the polarization effect of randomly polarized light whichis conventionally used as exposure light may reduce the image-formingperformance, and for this reason it is preferable to use polarizedirradiation. Linearly polarized light is irradiated in alignment withthe longitudinal direction of the line pattern of a line-and-spacepattern of a mask (reticule), and diffracted light of an S-polarizedlight component (TE-polarized light component), i.e., a polarizationdirection component along the longitudinal direction of the linepattern, is copiously emitted from the pattern of the mask (reticule).When the space between the projection optical system PL and thephotoresist applied to the substrate P is filled with liquid, thediffracted light of the contrast-enhancing S-polarized light component(TE-polarized light component) has higher transmittivity against theresist surface than when this space is filled with air (gaseous body),making it possible to achieve high resolution performance even when thenumerical aperture NA of the projection optical system exceeds 1.0. Itis even more effective to combine a phase-shift mask with aoblique-incidence illumination method (particularly a dipoleillumination method) which matches the longitudinal direction of theline pattern such as that disclosed in Japanese Unexamined PatentApplication, First Publication No. H6-188169.

When, for example, exposure light EL from an ArF excimer laser is usedby a projection optical system PL with a reduced magnification ofapproximately one-quarter in projecting a minute line-and-space pattern(e.g. line-and-space of approximately 25 to 50 nm) onto the substrate P,a waveguide effect allows the mask M to function as a polarizationplate, whereby more of the S-polarized component (TE-polarizedcomponent) is emitted from the mask M than diffracted light of acontrast-reducing P-polarized component (TM-polarized component); whileit is therefore preferable to use linearly polarized irradiation, highresolution performance can also be obtained by irradiating the mask Mwith randomly polarized light even if the numerical aperture NA of theprojection optical system PL is as large as between 0.9 and 1.3. Whenexposing an extremely minute line-and-space pattern of the mask M ontothe substrate P, although a wire grid effect may make the P-polarizedcomponent (TM-polarized component) larger than the S-polarized component(TE-polarized component), if, for example, exposure light EL from an ArFexcimer laser is used by a projection optical system PL with a reducedmagnification of approximately one-quarter in projecting aline-and-space of larger than 25 nm onto the substrate P, a waveguideeffect allows the mask M to function as a polarization plate, morediffracted light of the S-polarized component (TE-polarized component)is emitted from the mask M than diffracted light of the P-polarizedcomponent (TM-polarized component), and consequently, high resolutionperformance can be obtained even if the numerical aperture NA of theprojection optical system PL is as large as between 0.9 and 1.3.

Furthermore, in addition to illumination using linearly polarized light(S-polarized illumination) along the longitudinal direction of the linepattern of a mask (reticule), it is also effective to combine aoblique-incidence illumination method with a polarized lightillumination method which irradiating linearly polarized light in acircular tangential (circumferential) direction centered around anoptical axis, as disclosed in Japanese Unexamined Patent Publication,First Publication No. H6-53120. In particular, when the pattern of themask (reticule) include not only a line pattern extending in onepredetermined direction but also a line pattern extending in a pluralityof different directions, by combining an orbicular zone illuminationmethod with the polarized light irradiation method of irradiatinglinearly polarized light in the circular tangential direction around anoptical axis as disclosed in Japanese Unexamined Patent Publication,First Publication No. H6-53120 mentioned above, high resolutionperformance can be obtained even if the numerical aperture NA of theprojection optical system PL is large.

In this embodiment, the optical element 2 is attached to the frontal endof the projection optical system PL, enabling the opticalcharacteristics of the projection optical system PL such as aberration(spherical aberration, coma aberration, etc.) to be adjusted using thislens. The optical element attached at the frontal end of the projectionoptical system PL may be an optical plate using in adjusting the opticalcharacteristics of the projection optical system PL. Alternatively, aparallel plane plate capable of transmitting the exposure light EL maybe used.

When the flow of the liquid LQ generates considerable pressure betweenthe substrate P and the optical element at the front end of theprojection optical system PL, instead of enabling the optical element tobe replaced, it may be firmly securely such that its does not move dueto this pressure.

While in this embodiment, the space between the projection opticalsystem PL and the substrate P surface is filled with the liquid LQ,another example is to attach a cover glass including the parallel planeplate to the surface of the substrate P and fill the space with theliquid LQ in this state.

While in this embodiment, the liquid LQ is water, other liquids may beused. For example, when the light source for the exposure light EL is anF₂ laser, since this F₂ laser light does not transmit through water, aliquid which F₂ laser light can be transmitted through may be usedinstead, e.g. perfluorinated polyether (PFPE) or a fluorinated fluidsuch as fluorinated oil. In this case, liquid affinity treatment may beperformed by forming a thin film of, for example, a substance havinglow-polarity molecular structure including fluorine in the portion whichcontacts the liquid LQ. In addition, a fluid which can transmit theexposure light EL, has a refractive index as high as is possible, and isstable with respect to the photoresist applied to the projection opticalsystem PL and the substrate P surface (e.g. cedarwood oil) can be usedas the liquid LQ. Surface-treatment in this case is similarly performedin accordance with the polarity of the liquid being used.

Note that as the substrate P of each of the above embodiments it ispossible to use not only a semiconductor wafer for manufacturing asemiconductor device, but also a glass substrate for display device, aceramic wafer for thin-film magnetic head, or an original plate(synthetic quartz, silicon wafer) for a mask and a reticule used in anexposure apparatus, etc.

As the exposure apparatus EX, in addition to a scanning-type exposureapparatus (scanning stepper) using a step-and-scan method ofscanning/exposing a pattern of the mask M while moving the mask M insynchronism with the substrate P, it is possible to utilize a projectionexposure apparatus (stepper) using a step-and-repeat method of exposingthe pattern of the mask M while the mask M and the substrate P are keptstationary, and then moving the substrate P in sequential steps. Theinvention can also be applied in an exposure apparatus which uses astep-and-switch method of transferring at least two partiallyoverlapping patterns on the substrate P.

The invention can also be applied in a multi-stage exposure apparatuswhich includes a plurality of substrate stages capable of holdingsubstrates for processing, such as wafers. For example, structures andexposure operations of a twin stage exposure apparatus including twosubstrate stages are disclosed in, for example, Japanese UnexaminedPatent Publications, First Publication Nos. H10-163099 and H10-214783(corresponding U.S. Pat. Nos. 6,341,007, 6,400,441, 6,549,269, and6,590,634), Published Japanese Translation No. 2000-505958 of the PCTInternational Publication (corresponding U.S. Pat. No. 5,969,441) orU.S. Pat. No. 6,208,407, the contents of which are incorporated hereinwithin the limits permitted by national regulations of countriesdesignated or elected in this international application.

While the above embodiment uses an exposure apparatus where a spacebetween the projection optical system PL and the substrate P is filledwith a liquid, the invention can also be applied in an immersionexposure apparatus which performs exposure while the entire surface ofthe substrate, which is the target of exposure, is covered with theliquid. Structures and exposure operations of an immersion exposureapparatus wherein the entire surface of the substrate, which is thetarget of exposure, is covered with liquid are disclosed in detail in,for example, Japanese Unexamined Patent Publications No. H6-124873 andH10-303114, U.S. Pat. No. 5,825,043, etc., the contents of which areincorporated herein within the limits permitted by national regulationsof countries designated or elected in this international application.

The type of the exposure apparatus EX is not limited to an exposureapparatus for manufacturing semiconductor element which exposes asemiconductor element pattern on the substrate P, and can be widelyapplied in exposure apparatuses for manufacturing liquid crystal displayelements and displays, exposure apparatuses for manufacturing thin-filmmagnetic heads, charge-coupled devices (CCD), or exposure apparatusesfor manufacturing masks and reticules, etc.

When using a linear motor in the substrate stage PST and the mask stageMST (see U.S. Pat. No. 5,623,853 and U.S. Pat. No. 5,528,118), it ispossible to use an air suspension type using an air bearing and amagnetic suspension type using Lorentz force or reactance force. Thestages PST and MST may be types which move along guides or guidelesstypes which do not include guides.

As the drive mechanisms of the stages PST and MST, it is possible to useplane motors which drive the stages PST and MST by means ofelectromagnetic force generated by a magnet unit including magnetsarranged in two dimensions and an electromechanical unit including acoil arranged in two dimensions, these units being arranged oppositeeach other. In this case, either one of the magnet unit and theelectromechanical unit is connected to the stages PST and MST, and theother one is provided on the moving face side of the stages PST and MST.

Reactive force generated by the motion of the substrate stage PST may bemechanically allowed to escape to the floor (ground) using a framemember such that it is not transmitted to the projection optical systemPL, as described in Japanese Unexamined Patent Publication, FirstPublication No. H8-166475 (U.S. Pat. No. 5,528,118).

Reactive force generated by the motion of the mask stage MST may bemechanically allowed to escape to the floor (ground) using a framemember such that it is not transmitted to the projection optical systemPL, as described in Japanese Unexamined Patent Publication, FirstPublication No. H8-330224 (U.S. Pat. No. 5,874,820).

As described above, the exposure apparatus EX of this embodiment ismanufactured by assembling various types of subsystems which contain theconstituent elements described in the patent claims in such a manner asto maintain predetermined mechanical, electrical, and optical precision.To maintain these types of precision, adjustments to achieve opticalprecision of the various optical systems, adjustments to achieveelectrical precision of the various electrical systems, and adjustmentsto achieve mechanical precision of the various mechanical systems aremade before and after assembly. The assembly step from the various typesof subsystems to the exposure apparatus include mechanical connection,wiring of electrical circuits, piping of atmospheric pneumatic circuits,and so on, between the various subsystems. Of course, individualassembly steps of each of the subsystems are performed prior to thisassembly step from the various subsystems to the exposure apparatus.When the assembly step from the various subsystems to the exposureapparatus is completed, overall adjustments are made to ensure thevarious types of precision of the entire exposure apparatus. Preferably,the exposure apparatus is manufactured in a clean room whosetemperature, cleanliness, and the like are managed.

As shown in FIG. 4, a micro device such as a semiconductor device ismanufactured by a step 201 of designing functions/performance of themicro device, a step 202 of producing a mask (reticule) based on thedesign step, a step 203 of producing a substrate which forms the basematerial of the device, an exposure processing step 204 of transferringthe pattern of the mask onto the substrate by exposure using theexposure apparatus EX of the embodiment described above, a deviceassembly step (including dicing, bonding, and packaging steps) 205, aninspection step 206, and so on.

1. An exposure apparatus which exposes a substrate by irradiatingexposure light onto a substrate via a projection optical system and aliquid, comprising: a liquid supply mechanism that supplies the liquid;and a measuring device which measures a time during which the supply ofthe liquid from the liquid supply mechanism is stopped.
 2. The exposureapparatus according to claim 1, wherein the supply of the liquid fromthe liquid supply mechanism is restarted when the stopping time exceedsa predetermined allowable time.
 3. The exposure apparatus according toclaim 2, wherein the liquid supply mechanism comprises a flowpath thatsupplies the liquid, and the allowable time is determined taking aproliferation time of bacteria in the flowpath into a consideration. 4.The exposure apparatus according to claim 2, wherein the exposure lightis irradiated onto the substrate with an end face of the projectionoptical system contacting the liquid; and the allowable time isdetermined taking a drying time of liquid stuck to the end face of theprojection optical system into a consideration.
 5. The exposureapparatus according to claim 4, wherein the allowable time is determinedsuch that impurities do not stick to the end face of the projectionoptical system due to drying of the liquid on the end face.
 6. Theexposure apparatus according to claim 4, wherein the supply of theliquid from the liquid supply mechanism is restarted such that the endface of the projection optical system contacts the liquid.
 7. Theexposure apparatus according to claim 2, further comprising a substratestage which holds the substrate; and wherein, when the allowable time isexceeded, the supply of the liquid from the liquid supply mechanism isrestarted with the projection optical system being arranged facing aflat section of the substrate stage.
 8. The exposure apparatus accordingto claim 7, wherein the supply of the liquid from the liquid supplymechanism is restarted with the substrate or a dummy substrate held onthe substrate stage.
 9. The exposure apparatus according to claim 1,wherein the liquid is pure water.
 10. The exposure apparatus accordingto claim 1, wherein the liquid supply mechanism comprises a flowpaththat supplies the liquid and a valve for opening and closing theflowpath; and the stop of the supply of the liquid from the liquidsupply mechanism is determined from an operation of the valve.
 11. Theexposure apparatus according to claim 1, wherein the liquid supplymechanism comprises a flowpath that supplies the liquid and a flow meterthat measures an amount of flow of the liquid along the flowpath; andthe stop of the supply of the liquid from the liquid supply mechanism isdetermined based on a measurement result of the flow meter.
 12. Theexposure apparatus according to claim 2, wherein the supply of theliquid from the liquid supply mechanism is restarted with the projectionoptical system facing a predetermined object.
 13. The exposure apparatusaccording to claim 12, wherein the object comprises a stage which canmove along the end face of the projection optical system.
 14. A devicemanufacturing method comprising: using the exposure apparatus accordingto claim
 1. 15. A maintenance method of a projection optical systemwhich projects an image of a pattern via a liquid, comprising: measuringan elapsed time from when an end face on an image surface side of theprojection optical system becomes in an immersed state to when itbecomes a non-immersed state.
 16. The maintenance method according toclaim 15, further comprising wetting the end face on the image surfaceside of the projection optical system with the liquid when the elapsedtime exceeds a predetermined allowable time.
 17. An exposure methodcomprising: exposing, by using a projection optical system maintainedusing the method according to claim 15, a substrate to light byprojecting an image of a device pattern via liquid onto the substrate.